From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B296EC12002 for ; Wed, 21 Jul 2021 12:25:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E2916120F for ; Wed, 21 Jul 2021 12:25:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237494AbhGULpB (ORCPT ); Wed, 21 Jul 2021 07:45:01 -0400 Received: from lb3-smtp-cloud7.xs4all.net ([194.109.24.31]:46547 "EHLO lb3-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231680AbhGULpA (ORCPT ); Wed, 21 Jul 2021 07:45:00 -0400 Received: from cust-b5b5937f ([IPv6:fc0c:c16d:66b8:757f:c639:739b:9d66:799d]) by smtp-cloud7.xs4all.net with ESMTPA id 6BI6mheQn2bXB6BI7mDvh4; Wed, 21 Jul 2021 14:25:36 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xs4all.nl; s=s2; t=1626870336; bh=+DztvelO/yPgK1wYCM6vfTtwlapzEajeVBirBtT85+c=; h=Subject:To:From:Message-ID:Date:MIME-Version:Content-Type:From: Subject; b=owxEOz2JVJgHnjkVvoTs0ZPVyBWgG5pUAKJFHmx4IliqUiSgkpouY0yQPGjH79l7B 6fPNBIphMzRitU28Rwb+ELlVPfQzjpqC8aPlU2SKgyI+VMKo5QdCwxHs0mlL/BpqKD x+b51h4N598k2n/dItwCZQ40Sab4MrMVrohkLPuydwq0Y2s2nuHv4z5sgY6YxmXSaV Z0OISIqcZ3V3haA1QHaM83x2iXNkLedUfVXvHKiimwE82eYIlO9PbT6R2Ypka0vb0X YvwhZA5H0RG/tezrRNn9ON4/XW8jWjJsN3Tse4Tz1GIXED4THpNfHlMf0uZx3F382Y cAd972MIu4Csw== Subject: Re: [PATCH] media: em28xx: fix corrupted list To: Pavel Skripkin Cc: mchehab@kernel.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com References: <20210706145025.25776-1-paskripkin@gmail.com> <20210721152154.6b1a4e68@gmail.com> From: Hans Verkuil Message-ID: <7df1705e-b2c7-ddfc-9cc5-582fb1a304e5@xs4all.nl> Date: Wed, 21 Jul 2021 14:25:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210721152154.6b1a4e68@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4xfFspLPSmV4+1cSenxF+ojR+5K7O9bPy1mqfVyHs2olKwfYvYxD4Rdd97Aro2hIHocUBs1rPVdp1Yy8OyRLlc3WMeL35CVpzrb7KAzztJO9tVzsTUqivi V9TRKA2XkfMAvd4BM5IEaYeyD40us2PmzTESWvHK0oH53Apu1wzAtXqgvePfnzDXGtvLt6K87F35093hBCZglltkhoj4T8zcE32m2gxq6AJoM6ln6BLI6uWf Pkz5+LFNUMx1lcVmP72RT00JWIwQPzf09DT6PvVclQEVU8pQlhu0gayqXJI7/vI6eSKrj/Tbm0SaFdwU7ShT3EWGB3OsGZOUS3N86L2+wH53qZ3qofr61JTj umKG5WezCpcQUw5Boq3x+dCwn1HONCW6pdcl96Oo4uez+vZoyi2f4umFN1uVGPZHU8r373ukViiKWTy8MLKcvP1KlO6L6yJmEHZg1Fmrrh5X+dYcESsM8Ozl 583KWzwLX0Ubwq0x Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/07/2021 14:21, Pavel Skripkin wrote: > On Tue, 20 Jul 2021 14:13:13 +0200 > Hans Verkuil wrote: > >> On 06/07/2021 16:50, Pavel Skripkin wrote: >>> Syzbot reported corrupted list in em28xx driver. The problem was in >>> non-reinitialized lists on disconnect. Since all 2 lists are global >>> variables and driver can be connected and disconnected many times we >>> should call INIT_LIST_HEAD() in .disconnect method to prevent >>> corrupted list entries. >>> >>> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code >>> to a proper place") Reported-by: >>> syzbot+a6969ef522a36d3344c9@syzkaller.appspotmail.com >>> Signed-off-by: Pavel Skripkin --- >>> drivers/media/usb/em28xx/em28xx-cards.c | 2 ++ >>> drivers/media/usb/em28xx/em28xx-core.c | 6 ++++++ >>> drivers/media/usb/em28xx/em28xx.h | 1 + >>> 3 files changed, 9 insertions(+) >>> >>> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c >>> b/drivers/media/usb/em28xx/em28xx-cards.c index >>> ba9292e2a587..8b1ff79c37a0 100644 --- >>> a/drivers/media/usb/em28xx/em28xx-cards.c +++ >>> b/drivers/media/usb/em28xx/em28xx-cards.c @@ -4148,6 +4148,8 @@ >>> static void em28xx_usb_disconnect(struct usb_interface *intf) >>> dev->dev_next = NULL; } >>> kref_put(&dev->ref, em28xx_free_device); >>> + >>> + em28xx_reset_lists(); >>> } >>> >>> static int em28xx_usb_suspend(struct usb_interface *intf, >>> diff --git a/drivers/media/usb/em28xx/em28xx-core.c >>> b/drivers/media/usb/em28xx/em28xx-core.c index >>> 584fa400cd7d..03970ed00dba 100644 --- >>> a/drivers/media/usb/em28xx/em28xx-core.c +++ >>> b/drivers/media/usb/em28xx/em28xx-core.c @@ -1131,6 +1131,12 @@ >>> void em28xx_init_extension(struct em28xx *dev) >>> mutex_unlock(&em28xx_devlist_mutex); } >>> >>> +void em28xx_reset_lists(void) >>> +{ >>> + INIT_LIST_HEAD(&em28xx_devlist); >>> + INIT_LIST_HEAD(&em28xx_extension_devlist); >> >> This needs a mutex_lock(&em28xx_devlist_mutex); >> >> But actually, I don't think this is right: if there are multiple >> em28xx devices, then I think if you disconnect one, then the other is >> - with this code - also removed from the list. >> >> Can you give a link to the actual syzbot bug? I'm not at all sure you >> are fixing the right thing here. > > Hi, Hans! > > I guess, I missed my coffee that morning, sorry :) This patch looks > complety wrong, of course. > > I've took a close look at this bug one more time, and I found the true > root case of this bug. > > If em28xx dev has dev_next pointer we need to close dev->next extension > on disconnect to avoid UAF and corrupted list bug. So, something like > this should work: > > diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c > index c1e0dccb7408..d56b040e1bd7 100644 > --- a/drivers/media/usb/em28xx/em28xx-cards.c > +++ b/drivers/media/usb/em28xx/em28xx-cards.c > @@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf) > > em28xx_close_extension(dev); > > - if (dev->dev_next) > + if (dev->dev_next) { > em28xx_release_resources(dev->dev_next); > + em28xx_close_extension(dev->dev_next); > + } > em28xx_release_resources(dev); > > if (dev->dev_next) { > > How to You feel about it? I am going to send this patch for syzbot > testing That looks a lot saner :-) > > > Syzbot link: > https://syzkaller.appspot.com/bug?id=3609bbf45bf63a8f6032f330eb3d34f51cc81493 > > > Again, sorry for v1 patch, I don't know how I came up with this fix :( No problem, just post a v2 if syzbot passes. Regards, Hans > > > > With regards, > Pavel Skripkin >